Generator smell like burning rubber

[TN Jen]

2014 Jayco 32DC, class c, 32 ft
Generator: Onan 4000

The RV is in storage; its winterzied and undercover at a secure storage facility. A few days ago I went over to run the engine and generator for its monthly check. Both ran just fine for about 15 minutes. Then the generator turned off and when I went to check on it from the outside panel, it smelled like burning rubber. There was no smoke or signs of problem, except for a small drop (the size of two tic tac candies) of smelly burnt goo sitting inside the main panel. The location of the smelly goo was odd because it was not near any moving part, not near any rubber, etc. I checked the entire area around it and could not figure out where it came from. It was not a drip, so perhaps it got flung off and landed in that spot (?). Attached is a photo to show the general location. This picture is NOT my own generator - its something I grabbed from Google- but its close enough to demonstrate the general area where I found the burnt goo. I could not find any other issues. The main coach gas tank was nearing 1/4 tank, so I thought maybe it was shut down or had a problem by being starved of fuel. Anyway, I closed up the RV that day and left it alone.

Today I went back to check on it and put some gas in the main coach gas tank. After I gassed it up, I tried the generator and it will fire and turn over but it won't catch and stay on. When it cranks and turns over, it sounds normal, it sounds like it is going to turn on, but it just wont keep going, like its not getting fuel. I removed the panel and checked all around with no obvious signs of problems. Checked the oil and its fine. I had a routine service done probably 10 hours ago. The main light panel is blinking indicating 'service'.

Before I schedule a visit to the repair shop I thought I would check if folks had ideas. I have heard people talk about 'vapor lock' but I dont know what that means and if it would have caused the burning smell. This system has worked like a charm until now. It probably has about 110 hours.

Thanks!

[WinnieView]

Is there a cloth cover touching the exhaust pipe?

[RogerR]

If that is the controls for the generator you may have a bad electrical item. Pull the cover when not running and not plugged in and see if anything inside looks burnt.

[TN Jen]

There is no cloth cover (or other cover) on the exhuast pipe.

Originally Posted by WinnieView

Is there a cloth cover touching the exhaust pipe?

[TN Jen]

Originally Posted by WinnieView

Is there a cloth cover touching the exhaust pipe?

Please note that photo is not of my actual generator, which is a tad different. But tomorrow I will go over and try find the area with the electrical circuits and examine if for damage.

Its just weird because I cannot figure out where the little drop of burnt goo came from.

[TN Jen]

Problem identified and fixed: burned out control board.

It was indeed the master control board. For those unfamiliar, the control board is the electronic 'brain' of the generator, that looks like a typical computer circuit board, with little wires and nodes. Board is enclosed in a plastic case.

I don't know why, but the control board 'failed', meaning it burned up somehow, which caused the burning smell and the drop of burnt residue I found. The burned residue had not dripped onto the spot I found it, rather, it had been pushed out of the control board through a small gap in the edge of the plastic case. I could not originally identify this because the old control board was so covered in grime and dust I could not see the circuitry inside of it, and I thought it was simply a black piece of plastic. I did not realize I was looking at the control board.

Anywho, all fixed, for a grand total of $1100. Gulp. The part itself was $700. And while I am eager to attempt a lot of repairs, myself, I would never try this level of expertise.

Attached is a photo reference. This is NOT my actual generator, but its close enough for learning purposes. The red circle identified the control board.

Hope this helps someone else!

[Siamese]

Ouch.

[oldmanAZ]

Thanks for letting everyone know what the problem was and the resolution.

[brooklynchuck]

TN Jen, thank you for this post. This started happening to me a week ago and I originally thought it was dripping oil or even condensed fuel. Those pix you shared and the description explain exactly what I'm experiencing. Although today, the damn control board blew that goopy corner straight off and shut the generator down! Lolz

Anyway, I'm looking up replacement control boards and will give the self-repair a try. Looks like the parts cost will be about $300....wish me luck and

THANKS AGAIN for helping me figure it out two years in advance